It happened around 6:15 a.m. Thursday in the 7100 block of Seaford Avenue in Upper Darby, Pa.
Investigators tell Action News the suspect, who has not yet been identified, was just released from Graterford Prison eight days ago.
He went to see his ex-girlfriend, who police said was going to, quote, "hook back up" with him.
When he came into the house, investigators said he found her in bed with another man. Police say he took out two knives that he had on him and stabbed both his ex and her lover multiple times.
Both were taken to the Hospital of the University of Pennsylvania in critical condition.
The suspect fled, but was later captured.
More details are expected Thursday afternoon.